Network coding is a specific channel coding known as rateless coding. The transmission model between the transmitting end and the receiving end is relatively simple: The transmitting end sends code packets to the receiving end continuously at the greatest rate, without waiting for feedback information from the receiving end; and the receiving end obtains original data after accumulating enough code packets.
In abstract algebra, a Galois field (also known as a finite field) is a field that includes a finite number of elements (digits). A Galois Field (GF) composed of q elements may be expressed as GF (q). GF operation is defined as a specific cyclic mapping relation between finite elements. Typical GF operations include GF addition and GF multiplication. Due to characteristics of circulation, the finite elements in the GF are correlated with each other to form a finite loop. For any element outside this loop, a modulo operation is performed on the element outside the loop so that the element is mapped to an element in the finite loop. The addition table and the multiplication table of the GF are globally unique. Reverse operation of the GF addition and multiplication exists because the GF addition and multiplication operations are one-to-one mappings. GF(q) addition and multiplication are expressed as:A⊕B=(A+B)mod q AB=(A×B)mod q 
In the formulas above,  is an adding operator in the GF,  is a multiplying operator in the GF, and mod refers to modulo operation.
In the coding process and the decoding process of the network codes, the original data blocks are operated by performing the GF addition and the GF multiplication. Because the operation in the GF is completely reversible, the decoding process is a reverse process of the coding process.